Satellite mini-dish multi-switches have been available since the introduction of Dual Low Noise Block (LNB) mini-dish systems. An LNB receives a 10 GHz signal from an orbiting satellite and converts that signal down to 950-1450 MHz for reception by the mini-dish receiver. A dual LNB mini-dish system allows consumers with several receivers to receive multiple satellite signals in their home. The primary function of the multi-switch is to allow a dual LNB digital satellite mini-dish system's signal to be distributed to multiple mini-dish receivers, typically four or eight.
There are many multi-switches in the marketplace today. There are multi-switches with inputs for the A and B-side of a dual LNB system with four or eight outputs. There are multi-switches that also incorporate an outdoor VHF/UHF terrestrial antenna input for distribution to the same four or eight outputs. Amplified multi-switches, like the subject of the present invention, amplify the satellite signals and are necessary to compensate for splitter loses.
The basic function of a multi-switch is as follows. The multi-switch has an A input side rated at 13V/14V DC and a B input side rated at 17V/18V DC. Every time that a channel is changed, the satellite receiver sends either 13 or 17 volts up the coaxial cable to the multi-switch. The multi-switch detects which voltage is sent by means of a sensor and selects the appropriate LNB. The LNB routes the appropriate signal to the designated receiver. A multi-switch with antenna input will also combine the lower 50-800 MHz terrestrial antenna signals with the satellite signal for use with a single coaxial cable. It is then separated at the receiver by the use of a satellite diplexer.
All current satellite multi-switches allow DC voltage to travel up to the A and B inputs for power. However, DC voltage is not supplied to the terrestrial antenna port and hence the outdoor antenna. The main reason for this is that it is not desirable for voltage to reach a passive antenna. Voltage going to a passive antenna would distort the image. For this reason, there has never been a DC path mechanism in place for the terrestrial antenna port of a multi-switch.
There are negative aspects of not having a DC path mechanism to the terrestrial antenna port. Amplified outdoor antennas require the use of a power injector to supply DC voltage through the coaxial cable to the amplifier circuit, which is located in the antenna housing. As shown in FIG. 1, a consumer using an amplified outdoor antenna 118, requiring voltage for proper operation, and a conventional multi-switch 110, would need to place a power injector 120 between the antenna and the multi-switch. This would necessitate placing the power injector either outside or in an attic, since most cable junctions are located at those locations. These are not the most convenient or safest locations for electrically powered components.
Accordingly, there is a substantial interest in the industry for a Dual LNB multi-switch with a terrestrial antenna port that would allow a consumer to inject DC voltage from the power injector to the amplified antenna, while preventing this DC voltage from reaching a passive antenna.